Conventionally, a lighting fixture having an LED unit (LED lighting fixture) has been proposed (for example, Japanese Patent Application Publication Nos. 2003-59330 and 2008-258066 (JP2003-59330A and JP2008-258066A)).
The LED lighting fixture disclosed in JP2003-59330A has an LED module board 37 on which LED chips 36, etc. are mounted, as shown in FIG. 15. On the LED module board 37, a terminal block 24 having terminals 39 used for directly connecting feeder wires 38 to the LED module board 37 is provided. In the terminal block 24, release buttons 25 for releasing the feeder wires 38 from the respective terminals 39 are provided. Further, in the LED lighting fixture having the LED module board 37, the LED chips 36, the LED module board 37, the terminal block 24 and the like constitute an LED unit.
Further, the LED lighting fixture disclosed in JP2008-258066A is, for example, a pendant light that is a lighting fixture suspended from a ceiling. As shown in FIGS. 16A and 16B, this LED lighting fixture includes an LED board 27 having LEDs 26 thereon, and a power circuit 28 for supplying electricity to the LED board 27. This LED lighting fixture further includes a cylindrical LED casing 29 having a base for holding the LED board 27, and a cylindrical power casing 30 for holding a power circuit 28. The power casing 30 is separated from the LED casing 29 and has a base. Further, the power casing 30 is placed above the LED casing 29.
In a bottom wall 30c of the power casing 30, there is a cord passing hole 30d through which a power-side cord 32 electrically connected to the power circuit 28 can pass. The distal end of the power-side cord 32 is provided with a connection plug 32a. Further, locking hooks 34 used for holding the LED casing 29 protrude from the lower surface of the power casing 30. The locking hooks 34 are arranged at regular intervals in a circumference direction.
An upper plate 29a is attached to the In the LED casing 29 to close the space defined in the LED casing 29. The upper plate 29a has a cord passing hole 29b through which an LED-side cord 33 electrically connected to the LED board 27 passes. At the leading end of the LED-side cord 33, a connection plug 33a that is removably connected to the connection plug 32a of the power-side cord 32 is provided. Further, in the upper plate 29a, locking holes 35 are formed correspondingly to the locking hooks 34 of the power casing 30 so that the locking hooks 34 can be engaged with the respective locking holes 35. Accordingly, the LED lighting fixture having the construction shown in FIGS. 16A and 168 can be assembled by bringing the upper plate 29a of the LED casing 29 into surface contact with the bottom wall 30c of the power casing 30. Further, in the LED lighting fixture having the construction shown in FIGS. 16A and 168, the LEDs 26, the LED board 27, the LED casing 29, the upper plate 29a, the LED-side cord 33 and the connection plug 33a constitute an LED unit.
However, considering the LED unit is used in a variety of environments, it is preferred that the LED unit be provided with a sealing structure capable of preventing moisture or impurities from being introduced into the LED unit. Here, although it is not related to an LED unit, there has been proposed, as a structure for improving the watertightness between a pair of housing bodies, a sealing structure that is a packing formed by hardening a sealing material filled in a groove of one of the pair of housing bodies with a space provided between the sealing material and one side surface of the groove by using a jig (for example, Japanese Patent Application Publication No. H11-340648 (JP11-340648A)). Another sealing structure that is formed by applying a silicone resin having a lower hardness in a groove of one of a pair of housing bodies and by applying another silicone resin having a higher hardness on the silicone resin having the lower hardness and is used as a seal between the pair of housing bodies has been proposed (for example, Japanese Patent Application Publication No. H10-324360 (JP10-324360A)). A further sealing structure that is formed by placing a separately produced annular packing in an annular groove defined in a pair of housing bodies engaged with each other has been proposed (for example, Japanese Patent Application Publication No. 2010-252224 (JP2010-252224A)). Still another sealing structure that is formed by placing spherical sealing materials in a groove of one of a pair of housing bodies has been proposed (for example, Japanese Patent Application Publication No. 2010-251616 (JP2010-251616A)).
However, in each of the sealing structures disclosed in JP11-340648A and JP10-324360A, a liquid sealing material is used. However, a long time is required to harden the sealing material after the sealing material is applied, so that it is problematic in that the long hardening time may reduce the productivity. Particularly, when the hardening time of the sealing material is too long, the housing bodies may not be appropriately sealed in desired locations due to unexpected vibration or external force applied to the housing bodies during an assembling process. Further, when the sealing material is being hardened, the sealing material may be deformed or bubbles may be formed in the sealing material so that close contact between the housing bodies that are to be sealed by the sealing material may not be accomplished. Further, in the sealing structure disclosed in JP2010-252224A in which the annular packing is used to seal the housing bodies, a period of time is required to place the annular packing in the groove of the housing bodies, thereby resulting in a poor productivity. Further, when the annular packing is not precisely placed at a predetermined location in the groove of the housing body or the packing is placed in the groove in a deformed state, desired watertightness of the packing may not be accomplished. Further, in the sealing structure using the spherical sealing materials disclosed in JP2010-251616A, it is necessary to place a predetermined number of spherical sealing materials at predetermined locations in the groove and when any one spherical sealing material is not placed, desired watertightness may not be realized. Further, because it is necessary to place the predetermined number of spherical sealing materials in the groove without missing any one material, it is difficult to automatically place the sealing materials using an automated machine and work efficiency of manual assembly performed by a person is low, thus deteriorating the productivity.
Particularly, the LED unit may emit light from a light-emitting device through a lens provided in a cover. Further, when the sealing structure disclosed in each of JP11-340648A, JP10-324360A, and JP2010-251616A is used in an LED unit, the optical characteristics of the LED unit may be largely influenced by a positional error of the cover.